The invention relates to a circuit board having functions for measuring and adjusting intensity and a phase of a current flowing in a junction of the circuit board and an electronic apparatus or a casing and also relates to an electronic apparatus in which such a circuit board has been mounted.
In an electronic apparatus or the like, in order to specify a position of a current which becomes a cause of generation of an unnecessary electromagnetic radiation and an electromagnetic mutual interference path between electronic apparatuses or electronic circuits which becomes a cause of the erroneous operation, performance deterioration, or the like, a technique for measuring distribution of magnetic fields near the electronic apparatus is effective.
Generally, to specify the radiating position of the unnecessary electromagnetic radiation radiated from the circuit board sole body, by measuring the distribution of the neighboring magnetic fields on the circuit board by using a magnetic field probe, the position of the current which becomes the cause of generation of the radiation can be specified (for example, refer to JP-A-2002-156430). To specify the radiating position of the unnecessary electromagnetic radiation radiated from the electronic apparatus casing, by measuring the distribution of the magnetic fields near the casing, an examination similar to that for the circuit board sole body can be made.
As a technique for reducing the unnecessary electromagnetic radiation from the casing or the like, a method whereby a filter is inserted into a connecting portion between the circuit board and the casing or the like and intensity, a phase, and a frequency of a current flowing out to the casing or the like are controlled has been shown (for example, refer to JP-A-7-225634 and JP-A-10-190166).